According to the Doctor Who scriptwriters, well whoever wrote the script for 'City of Death' at least, none of us would be here at all now if it wasn't for the Jagaroth. Life on Earth was created when the Jagaroth spaceship exploded some 400 million years ago according to the story.
Being as it was the Jagaroth who inadvertently created us all in Doctor Who I find it highly perplexing that there has only ever been one story in the show featuring them (as far as I know).
Does anybody else have any views on the subject?